“I think there is a good there is a good bit of ambiguity now about which of these apps require FDA clearance,” he says. “I know a number of investors who are interested ion those businesses that are kind of nervous.”

Johnson & Johnson’s working on an app that would connect iPhones belonging to diabetics to their glucose monitors. And others believe an app for ultrasound is possible. But the FDA is watching. It’s already forced some firms to pull their medical apps down if they are unproven or make claims the companies can’t back up.

MIMvista created an app that would let radiologists view CT scans, MRIs and x-rays on their mobile phones. The app was slick and beatiful, and it caught the eye of Apple executives. They asked the company to present it at Apple’s world-wide developers conference in 2008.

The FDA was less impressed. Regulators expressed concerns that doctors would be viewing these images under very different conditions than they encountered in a radiology reading room. They asked the group the reapply. After nearly a year of waiting, the FDA decided this app was so new and different that before it could be approved, the firm that made it would have to test it with full-blown clinical trials.